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Clinical Microbiology Reviews Mar 2020Increases in tick-borne disease prevalence and transmission are important public health issues. Efforts to control these emerging diseases are frustrated by the struggle... (Review)
Review
Increases in tick-borne disease prevalence and transmission are important public health issues. Efforts to control these emerging diseases are frustrated by the struggle to control tick populations and to detect and treat infections caused by the pathogens that they transmit. This review covers tick-borne infectious diseases of nonrickettsial bacterial, parasitic, and viral origins. While tick surveillance and tracking inform our understanding of the importance of the spread and ecology of ticks and help identify areas of risk for disease transmission, the vectors are not the focus of this document. Here, we emphasize the most significant pathogens that infect humans as well as the epidemiology, clinical features, diagnosis, and treatment of diseases that they cause. Although detection via molecular or immunological methods has improved, tick-borne diseases continue to remain underdiagnosed, making the scope of the problem difficult to assess. Our current understanding of the incidence of tick-borne diseases is discussed in this review. An awareness of the diseases that can be transmitted by ticks in specific locations is key to detection and selection of appropriate treatment. As tick-transmitted pathogens are discovered and emerge in new geographic regions, our ability to detect, describe, and understand the growing public health threat must also grow to meet the challenge.
Topics: Animals; Clinical Laboratory Techniques; Humans; Tick-Borne Diseases; Ticks
PubMed: 31896541
DOI: 10.1128/CMR.00083-18 -
Infection and Immunity Sep 2022Ticks are hematophagous ectoparasites capable of transmitting multiple human pathogens. Environmental changes have supported the expansion of ticks into new geographical... (Review)
Review
Ticks are hematophagous ectoparasites capable of transmitting multiple human pathogens. Environmental changes have supported the expansion of ticks into new geographical areas that have become the epicenters of tick-borne diseases (TBDs). The spotted fever group (SFG) of frequently infects ticks and causes tick-transmitted rickettsioses in areas of endemicity where ixodid ticks support host transmission during blood feeding. Ticks also serve as a reservoir for SFG . Among the members of SFG , R. rickettsii causes Rocky Mountain spotted fever (RMSF), the most lethal TBD in the United States. Cases of RMSF have been reported for over a century in association with several species of ticks in the United States. However, the isolation of R. rickettsii from ticks has decreased, and recent serological and epidemiological studies suggest that novel species of SFG are responsible for the increased number of cases of RMSF-like rickettsioses in the United States. Recent analyses of rickettsial genomes and advances in genetic and molecular studies of provided insights into the biology of with the identification of conserved and unique putative virulence genes involved in the rickettsial life cycle. Thus, understanding -host-tick interactions mediating successful disease transmission and pathogenesis for SFG rickettsiae remains an active area of research. This review summarizes recent advances in understanding how SFG species coopt and manipulate ticks and mammalian hosts to cause rickettsioses, with a particular emphasis on newly described or emerging SFG species.
Topics: Animals; Humans; Ixodidae; Mammals; Rickettsia; Rickettsia Infections; Rocky Mountain Spotted Fever; Ticks
PubMed: 35993770
DOI: 10.1128/iai.00621-21 -
Nature Communications Feb 2021Understanding ecological niches of major tick species and prevalent tick-borne pathogens is crucial for efficient surveillance and control of tick-borne diseases. Here...
Understanding ecological niches of major tick species and prevalent tick-borne pathogens is crucial for efficient surveillance and control of tick-borne diseases. Here we provide an up-to-date review on the spatial distributions of ticks and tick-borne pathogens in China. We map at the county level 124 tick species, 103 tick-borne agents, and human cases infected with 29 species (subspecies) of tick-borne pathogens that were reported in China during 1950-2018. Haemaphysalis longicornis is found to harbor the highest variety of tick-borne agents, followed by Ixodes persulcatus, Dermacentor nutalli and Rhipicephalus microplus. Using a machine learning algorithm, we assess ecoclimatic and socioenvironmental drivers for the distributions of 19 predominant vector ticks and two tick-borne pathogens associated with the highest disease burden. The model-predicted suitable habitats for the 19 tick species are 14‒476% larger in size than the geographic areas where these species were detected, indicating severe under-detection. Tick species harboring pathogens of imminent threats to public health should be prioritized for more active field surveillance.
Topics: Animals; China; Cluster Analysis; Geography; Incidence; Species Specificity; Tick Infestations; Tick-Borne Diseases; Ticks
PubMed: 33597544
DOI: 10.1038/s41467-021-21375-1 -
Revue Scientifique Et Technique... Apr 2015Ticks are prominent parasites and competent vectors of pathogens that affect both humans and animals. This review outlines and illustrates the main features of the... (Review)
Review
Ticks are prominent parasites and competent vectors of pathogens that affect both humans and animals. This review outlines and illustrates the main features of the morphology of ticks of the families Ixodidae and Argasidae, and summarises the basic components of their life cycles. It focuses mainly on development processes and mortality among tick populations so as to provide an overview of how they are regulated in nature and how pathogens can be transmitted under such a framework. The effects of the weather on these life cycles are reviewed. The author also examines how landscape structure and biotic factors, such as the presence and abundance of hosts, may shape the density of tick populations. The uncertainty inherent in dealing with the transmission of pathogens by ticks is highlighted; this results from the sometimes complex relationships among the vectors, the climate and the presence and density of host populations. The need to obtain reliable field estimations of such relationships before drawing conclusions about the effects of the isolated components of the system is stressed. A section is devoted to addressing the expected (and not yet totally understood) effects of trends in climate on the spread of ticks, and how these can be analysed and tracked.
Topics: Animals; Arachnid Vectors; Communicable Diseases; Feeding Behavior; Ticks
PubMed: 26470449
DOI: 10.20506/rst.34.1.2345 -
Current Opinion in Insect Science Apr 2024As obligate blood-feeders, ticks serve as vectors for a variety of pathogens that pose threats on both human and livestock health. The microbiota that ticks harbor play... (Review)
Review
As obligate blood-feeders, ticks serve as vectors for a variety of pathogens that pose threats on both human and livestock health. The microbiota that ticks harbor play important roles in influencing tick nutrition, development, reproduction, and vector. These microbes also affect the capacity of ticks to transmit pathogens (vector competence). Therefore, comprehending the functions of tick microbiota will help in developing novel and effective tick control strategies. Here, we summarize the effects of main tick symbiotic bacteria on tick physiology and vector competency.
Topics: Animals; Humans; Ticks; Symbiosis; Tick-Borne Diseases; Bacteria
PubMed: 38244689
DOI: 10.1016/j.cois.2024.101163 -
Acta Virologica 2017Tick-borne viruses (TBVs) belong to the largest biological group known as arboviruses with unique mode of transmission by blood-feeding arthropods (ticks, mosquitoes,... (Review)
Review
Tick-borne viruses (TBVs) belong to the largest biological group known as arboviruses with unique mode of transmission by blood-feeding arthropods (ticks, mosquitoes, sand flies, biting midges, etc.) to a susceptible vertebrate host. Taxonomically, it is a heterogenous group of vertebrate viruses found in several viral families. With only one exception, African swine fever virus, all TBVs have a RNA genome. To date, at least 160 tick-borne viruses are known, some of them pose a significant threat to human and animal health worldwide. Recently, a number of established TBVs has re-emerged and spread to new geographic locations due to the influence of anthropogenic activities and few available vaccines. Moreover, new emerging tick-borne diseases are constantly being reported. Major advances in molecular biotechnologies have led to discoveries of new TBVs and further genetic characterization of unclassified viruses resulting in changes in TBVs classification created by the International Committee for the Taxonomy of Viruses. Although TBVs spend over 95% of their life cycle within tick vectors and the role of ticks as vectors has been known for over 100 years, our knowledge about TBVs and molecular processes involved in the virus-tick interactions is scarce.
Topics: Animals; Arachnid Vectors; Humans; Tick-Borne Diseases; Ticks; Virus Diseases; Virus Physiological Phenomena; Viruses
PubMed: 29186958
DOI: 10.4149/av_2017_403 -
Frontiers in Immunology 2021
Topics: Animals; Host-Parasite Interactions; Humans; Immunity; Tick-Borne Diseases; Ticks; Vaccines
PubMed: 34868085
DOI: 10.3389/fimmu.2021.796558 -
Frontiers in Cellular and Infection... 2018
Topics: Animals; Host-Pathogen Interactions; Humans; Immunity, Innate; Tick-Borne Diseases; Ticks; Transcriptome; Vaccines
PubMed: 29963500
DOI: 10.3389/fcimb.2018.00194 -
Parasite Immunology May 2021'Omics' technologies have facilitated the identification of hundreds to thousands of tick molecules that mediate tick feeding and play a role in the transmission of... (Review)
Review
'Omics' technologies have facilitated the identification of hundreds to thousands of tick molecules that mediate tick feeding and play a role in the transmission of tick-borne diseases. Deep sequencing methodologies have played a key role in this knowledge accumulation, profoundly facilitating the study of the biology of disease vectors lacking reference genomes. For example, the nucleotide sequences of the entire set of tick salivary effectors, the so-called tick 'sialome', now contain at least one order of magnitude more transcript sequences compared to similar projects based on Sanger sequencing. Tick feeding is a complex and dynamic process, and while the dynamic 'sialome' is thought to mediate tick feeding success, exactly how transcriptome dynamics relate to tick-host-pathogen interactions is still largely unknown. The identification and, importantly, the functional analysis of the tick 'sialome' is expected to shed light on this 'black box'. This information will be crucial for developing strategies to block pathogen transmission, not only for anti-tick vaccine development but also the discovery and development of new, pharmacologically active compounds for human diseases.
Topics: Animals; Genome; Host-Pathogen Interactions; Humans; Proteomics; Salivary Glands; Ticks; Transcriptome
PubMed: 33135186
DOI: 10.1111/pim.12807 -
Ticks and Tick-borne Diseases Jan 2021Over recent years, a multitude of pathogens have been reported to be tick-borne. Given this, it is unsurprising that these might co-exist within the same tick, however... (Review)
Review
Over recent years, a multitude of pathogens have been reported to be tick-borne. Given this, it is unsurprising that these might co-exist within the same tick, however our understanding of the interactions of these agents both within the tick and vertebrate host remains poorly defined. Despite the rich diversity of ticks, relatively few regularly feed on humans, 12 belonging to argasid and 20 ixodid species, and literature on co-infection is only available for a few of these species. The interplay of various pathogen combinations upon the vertebrate host and tick vector represents a current knowledge gap. The impact of co-infection in humans further extends into diagnostic challenges arising when multiple pathogens are encountered and we have little current data upon which to make therapeutic recommendations for those with multiple infections. Despite these short-comings, there is now increasing recognition of co-infections and current research efforts are providing valuable insights into dynamics of pathogen interactions whether they facilitate or antagonise each other. Much of this existing data is focussed upon simultaneous infection, however the consequences of sequential infection also need to be addressed. To this end, it is timely to review current understanding and highlight those areas still to address.
Topics: Animals; Coinfection; Humans; Prevalence; Tick-Borne Diseases; Ticks
PubMed: 33220628
DOI: 10.1016/j.ttbdis.2020.101607